Improvement in valvexgearing  for steam-engines



c NITED STATES JOHN W. HAOKWORTH, OF DARLINGTON, ENGLAND.

iMPROVEMENT IN VALVE-GEARING FOR STEAM-ENGINES.

Specification forming part of Letters Patent No. 133,529, dated December3, 1872.

specification:

It consists in the construction and combination of mechanism for workingthe valves of locomotive, marine, and other engines, whereby anydesirable amount of lead or advance,

deviating therefrom by an equal oscillatory movement on each side of thecenter line of action, from which oscillatory movement the motion of thevalve or valves is derived.

The following is a description of what I consider the best means ofcarrying out the invention: I employ an eccentricrod of moderate length,one end of which is formed into straps or clasps, which embrace aneccentric pulley secured to the main or driving shaft of the engine, theother end of the said eccentric rod being hinged, jointed, or attachedby suitable arrangements to'the pin of aslidingblock fitted to movefreely the full throw of the eccentric pulley in a path, which may bechanged to various angles. In one positionit lies in a plane, the axisof which falls through the center of the main or driving shaft. AtabouttWo-thirds of the length of the eccentric rod from the center ofthe straps, or one-third from the end of .the eccentric rod attached tothe sliding block,

the block moving in the before-named plane,

thereby communicating a certain proportion of oscillatory action of theeccentric rod which is derived from the throw of the eccentric pulley tothe valve. This amount is equal to the lap and lead. It constitutes thatwhich is termed the lead motion of the valve. As the extremes of thismovement occur when the engine is on the center, it determines therelative position of eccentric and main crank, and is suitable foreither back or forward working. The plane has hitherto been treated asfixed in a position central to that it will now be assigned to move in.This plane may take the form of a slot-hole cut through a shaft, orvarious other forms or modifications. The said shaft on which thebefore-named plane is formed is supported in bearings, the centers ofwhich are placed at a distance from the .main or driving shaft of theengine equal to the extreme centers of the eccentric rod. Further, thissaid shaft with the before-named plane formed on or attached thereto,may, with suitable rods and levers, be thrown to an angle of about fortydegrees on each side of the previouslyassigned center line, or any otherintermediate angular position, imparting through the medium of suchangular variation a variable and reverse lateral movement to that end ofthe eccentric rod moving in the hereinbefore-described plane, andthereby a proportionate increased movement to the valve.

This, then, is that part of my said invention which I designatevariable, traverse, and reverse motion, the greatest extremes of whichare produced when the lead motion is in the center of its action, thetwo movements being" Similar letters of reference indicate corre- Ispondin g parts in all the figures.

B is the main shaft, and b the single eccen tric required for myinvention. 0 is an eccen tric strap and rod, having the valve-rod connected at the point m. A is a portion of the stationary framing. One endof the eccentric rodhas, necessarily, themotion of the eccentric b. Theother end may be variously directed. It

' is provided with pin, D, which is formed with jaws on each side. Thesejaws embrace the two arms of an adjustable yoke or forked piece, E,which, being mounted on fixed trunnions 6, is capable of being adjustedat various inclinations to induce a corresponding motion of the adjacentend of the eccentric rod. The pin D is necessarily compelled toreciprocate in different paths, according as the piece E stands in acentral position or is inclined in one direction or the other. When thepiece E is adjusted in the positidn represented, so that the line oftravel of that end of the ec ceptric rod, if extended, would passthrough the main shaft B, the rod M leading to the valve-spindle, notrepresented, has a certain amount of motion equal to the lap andlead.This may be proportioned to any extent, according to the judgment of theengineer. If it be desired to increase the motion, when so conditioned,the pin we should be placed nearer the eccentric; but wherever it isplaced it is kept permanent. Now, if the piece E be inclined in onedirection or the other, so that the pin D shall have any up-and-downmotion, the engine will receive more steam at each stroke, and it willfollow the piston to a greater or less distance, according as theinclination of the piece E is increased or diminished. The inclinationof the piece E in one direction causes the engine to go ahead. Incliningit in the other direction causes it to go backward. The lead-and-lapmotion will be the same in amount and hold the same relative time inboth directions. The piece E may be held firmly in any position in whichit may be adjusted by means of the pinching-screw G standing in a curvedslot in the piece E. On slackin g this screw G the piece E may bechanged into any different position required. This change can beeffected by means of the worm H, operated by the hand-wheel H, andtaking in a curved rack or segment-teeth formed on the piece E, asshown. For locomotives and other small engines a link, operated by ahandlever, may be connected directly to the piece E so as to allow it tobe thrown instantlyinto various inclinations. For heavy engines it isbetter to employ a worm, as shown. There may be various other modes orforms for constructing the piece E. The trunnions may be enlarged toform wheels, and the pin D may be provided with rollers traversing ingrooves in such wheels instead of the jaws and bars represented. In somecases one such wheel with a deep groove and corresponding roller, or onesuch bar with strong jaws, taking hold of it might suifice. The frictionis considerably less with rollers than with jaws. The friction can bereduced still lower by providing long links pivoted on centers mountedon the adjustable pieceE, and if the links are made sufiiciently long sothat the path of the pinD does not differ sensibly from a right line thedevice will operate successfully. Any of the complex arrangements oflinks termed parallel motions may be used. The pinching-screw G may bedispensed with, but it is preferable to employ, it, as it gives vadesirable firmness to the entire work. The proportions of all the partsmay be varied, but it will be found that the yoke E, or equivalentguide-way, should never be inclined more than about forty de grees fromthe position represented. -It is essential that the valve-connection Mstand at right angles to the mean or central position of the eccentricrod, and that the-throw of the eccentric be always greater than is everrequired for the greatest throw of the valve.

I claim as my improvement in valve-gear-- The rod 0 operated by a crankor eccentric at one end, and reciprocating at the other end in achangeable path, having the valve-connection at an intermediate point,substantially as described, for producing two motions from one eccentriccrank or radialpin--one motion a for working that which is termed thelead of the valve, and the other motion at an angle with the former,whereby a variable expansion and reverse motion is obtained,substantially as herein specified.

In testimonywhereof I have hereunto set my hand this 16th day ofNovember, 1872, in the presence of two subscribing witnesses.

JOHN W. HAGKWORTH. Witnesses:

WM. (3. DEY, ALF. C. WES'IBROOK.

